class ReadStream{
    constructor(path,options={}){
        //放在实例上

        this.autoClose = options.autoClose||true;
        this.start = options.start || 0;
        this.end = options.end;

        this.highWaterMark = options.highWaterMark||64*1024
        this.open();
    }
    read(){
        const buffer = Buffer.alloc(this.highWaterMark);
        //读取文件中的内容 每次读取this.hightWaterMark个
        fs.read(this.fd,buffer,0,this.highWaterMark,this.highWaterMark,this.offset,(err)=>{
            if(byteRead){

            }
        });
    }
    open(){

    }
}